It has been recognized for some time that a combination of the PET (Positron Emission Tomography) and magnet resonance image recording modalities is expedient due to the advantageously complementary data. Therefore combined magnetic resonance/PET apparatuses have been proposed, with which it is possible to record accordingly co-registered magnetic resonance data and PET data at the same time.
However the problem arises that the activity of the magnetic resonance recording facility in some instances produces unintended interference with receiving on the PET side. This is due in particular to the high-frequency radiation transmitted by the magnetic resonance system and the gradient activity of the magnetic resonance system, which produces temporary interference in the PET components located within the magnetic resonance system.
To resolve such problems it has been proposed that the magnetic resonance components and the PET components should be shielded from one another. Such proposals are disclosed for example in DE 10 2007 007 623 A1 and DE 10 2005 015 071 A1. However such shielding is not always completely successful, so that the underlying problems remain even when the measures described there are applied.
The situation is complicated in that many such interference instances only occur sporadically, for example in certain states of the system as a whole or very specific magnetic resonance pulse sequences, which contain particular series of gradients or high-frequency pulses. Since further influencing factors, for example temperature, can also play a role, it is practically impossible to test all the theoretically possible states of the system and exclude any mutual influences.
Mutual influences become particularly disadvantageous when the PET data is falsified as a result, which can mean that a false diagnosis or no diagnosis at all is produced in a medical situation.